The National Institute on Drug Abuse (NIDA) supports research and development of new medications for the treatment of addiction. Medication development involves in vitro evaluations, non-clinical pharmacology and toxicology studies, pharmaceutical development, and clinical evaluations of potentiaal new medications for treating addiction. A critical aspect of the non-clinical evaluations involves characterizing the pharmacokinetics (PK) of the medication under development. Pharmacokinetics provides an assessment of the Absorption, Distribution, Metabolism, and Excretion (ADME) properties, which is critical in all phases of a fully integrated medication development program. The ADME studies provide supportive information to understand pharmacological effects and toxciological effects of a potential medication and its metabolites. Furthermore, the data generated from the ADME studies provide a basis for the selection of a proper animal model for pharmacological/toxicological evaluations, the selection of promising medications for clinical development, and rational design of dosage forms and dosage regimens. The non-clinical ADME studies for this contract typically include conducting the following: Bioavailability and pharmacokinetic studies, mass balance studies, tissue distribution studies, and toxicokinetic analysis of new potential medications. Additionally, this contract involves conducting analytical services which include structure identification of major metabolites by mass spectrometry or nuclear magnetic resonance(NMR) and the development of sensitive and specific assays for a potential medication and its metabolites in biological matrices using methods such as high performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), liquid chromatography with tandem mass spectrometry (LC/MS/MS), and gas chromatograph mass spectrometry (GCMS).